This invention relates generally to filter media and more particularly concerns melt-blown filter media for use in filtering liquids.
In a variety of industrial applications, it is necessary to provide a lubricating coolant to protect production machines from friction-created heat build-up, such as in the aluminum can manufacturing industry. As the lubricating coolant is used in connection with the manufacture of aluminum cans, the lubricating coolant becomes contaminated with metal particles, dirt, hydraulic oils, tramp oils, and lubricating oils. In order to assure the proper operation of the can forming machines, it is necessary to remove those contaminants from the lubricating coolant before it is recycled.
Conventionally, lubricating coolants have been filtered by cotton filters having fiber sizes of about 12 to 35 microns in diameter. One such filter medium is sold under the trademark Schneider 501. Also, the assignee of the present invention has manufactured and sold a non-woven polypropylene filter under the trademark Cyclean.RTM.. The Cyclean.RTM. filter comprises a laminate having a central layer of melt-blown polypropylene material sandwiched between external layers of spun-bonded polypropylene material.
It is important in filtering lubricating coolants to assure not only that the filter medium has an appropriate efficiency to filter out the contaminants from the lubricating coolant, but that the filter also provides effective filtration for a reasonable period of time before it becomes plugged and must be renewed.